Capacitive type ignition arrangement for internal combustion engines

ABSTRACT

Energy from a storage capacitor is transferred to an ignition capacitor when a first switch is made conductive, and the spark is initiated by discharge from the ignition capacitor through the ignition transformer upon closing of a second switch. The current limiting element between the storage capacitor and the ignition capacitor is an inductance.

0 finned Mates Patent 11 1 1111 3,782,353 Kamrnerer et a1. Jan. 1, 19741 CAPACITIVE TYPE IGNITION 3,372,681 3/1968 Phi11ips 123/148 EARRANGEMENT FOR INTERNAL 2,847,489 8/1958 Short 123/148 E 3,504,6584/1970 Chauls 123/148 E (:OMBUSTION ENGINES 3,465,738 9/1969 Ger1ach....123/148 E [75] Inventors: Heinz Kammerer, Nellingen; Heinz 3,045,148 7/162 McNulty 23/ 8 E Muller, Stuttgart, both of Germany ,392,192 1/1946Robinson 123/148 E 3,331,362 7/1967 Mitchel] 123/148 E 1 AssigneelRobert Bosch Gmbfl, Stuttgart, 3,489,129 1/1970 lssler 1 123/148 EGermany 3,316,449 4/1967 Quinn 123/148 E 22 F1 d: S t. 30, 1971 a i 1 le W Primary Examiner-Laurence M. Goodridge pp 135,162 AssistantExaminer-Ronald B. Cox

Attorney-Michael S. Striker [30] Foreign Application Priority Data Oct,6, 1970 Germany P 20 48 960.5 [57] ABSTRACT Energy from a storagecapacitor is transferred to an [52] 11.5. C1. 123/148 E, 123/148 gni i npa i or when a first switch is made conduc- [51] Int. Cl. F02 1/00 tivc,and h p rk i ini i ted y i charge from he [58] Field of Search 123/148 Eignition c pacit r through the ignition transformer upon closing of asecond switch. The current limiting [56] References Cited elementbetween the storage capacitor and the igni- UNITED STATES PATENTS 11011capacitor is an inductance. 3,312,860 4/1967 Strum 123/148 E 9 Claims, 3Drawing Figures CAPACITIVE TYPE IGNITION ARRANGEMENT FOR INTERNALCOMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates toignition arrangements for internal combustion engines. In particular, itrelates to such ignition arrangements wherein the storage capacitor isconnected to an ignition capacitor by means of a switching element and acurrent limiting element. Further, the ignition capacitor is connectedto an ignition transformer, more specifically the primary winding of theignition transformer via a second switch, while the secondary winding ofthe ignition transformer is connected to at least one spark plug. Thetwo switch elements are activated alternatingly.

A known arrangement of this type operates to generate a plurality ofsequential sparks. Specifically, a storage capacitor is charged from abattery through a DC. power supply. The energy stored in the storagecapacitor is transferred to the ignition capacitor through the currentlimiting element when the first switch means are in the conductivestate. The current limiting impedance is a resistance. At the desiredignition time, the ignition capacitor is discharged through the primaryof the ignition transformer thereby inducing a spark in the spark plugor in other spark generating element in the secondary winding. Theprimary winding of the ignition transformer does not load the powersupply, since at the time the second switch is closed, the first switchis opened.

The above-described ignition arrangement has the disadvantage that eachtransfer energy from the storage capacitor to the ignition capacitorcauses a loss of the energy in the current limiting resistance. Thus theefficiency of such an arrangement is very low. Such an arrangement isonly functional when a DC. power supply of high power output at a highvoltage is used.

SUMMARY OF THE INVENTION It is an object of the present invention toimprove the efficiency of the above-described ignition arrangement,thereby decreasing the necessity for a high supply voltage byutilization of the available energy.

The present invention comprises storage capacitor means and ignitioncapacitor means. An ignition transformer has a primary and a secondarywinding. The secondary winding of the ignition transformer is connectedto spark generating means, while its primary winding is connected inparallel with the ignition capacitor through second switch means, whensaid second switch means are in the conductive state. The ignitioncapacitor is connected to the storage capacitor through first switchmeans. The current limiting element connected in series with the firstswitch means comprise an inductance.

The use of the inductance causes almost lossless transfer of energybetween the storage and the ignition capacitor. Further, the presence ofthe inductance causes a resonant voltage rise across the capacitor, sothat the voltage available across the primary winding of the ignitiontransformer at ignition time is substantially higher than the voltageexisting across the storage capacitor. With appropriate design of theignition transformer and the inductance, the ignition arrangement may bedirectly connected to the battery, without use of a DC. power supply.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to the construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I shows an ignition arrangement inaccordance with the present invention, wherein an inductance is used;

FIG. 2 shows an ignition arrangement wherein a second primary winding ofthe ignition transformer serves as current limiting element; and

FIG. 3 shows an ignition arrangement wherein the primary winding of asecond ignition transformer serves as inductive impedance in the energytransfer circuit between the storage and the ignition capacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of thepresent invention will now be described with reference to the drawing.

The source of energy for the ignition arrangement shown in FIG. 1 is abattery 10 which is connected to a DC. power supply stage 11. The outputof this stage is connected to a storage capacitor 12 of microfarads. Itis further connected with first switch means, here a thyristor 13.Connected in series with thyristor 13, is an inductive impedance 14 andan ignition capacitor 15 of one microfarad. The primary winding 16a ofan ignition transformer 16 is connected in parallel with ignitioncapacitor 15 via second switch means, namely a thyristor 17. A sparkplug 18 is connected to the secondary winding 16b of the ignitiontransformer I6. The spark plug 18 is of course located in a cylinder ofthe internal combustion engine, which is not shown. A diode 19 isconnected, with opposing polarity, in parallel with thyristor 17.

In this arrangement, capacitor 12 is constantly charged to the outputvoltage of stage Ill. When thyristor 13 becomes conductive through acontrol voltage applied at its gate, a part of the electrical energystored in storage capacitor 12 is transferred through thyristor l3 andinductance 14 to the ignition capacitor 15. The inductive impedance 14in series with ignition capacitor 15 forms a series-resonant circuit,thus causing the voltage across the capacitor 15 to exceed the voltageacross capacitor 12. At this time the current through the circuit goesto zero, blocking thyristor 13. At the ignition time, the second switch,thyristor 17, becomes conductive causing the energy stored in ignitioncapacitor 15 to be discharged through the primary winding 16a ofignition transformer 16 and thyristor 17. This causes a high voltagepulse to be induced in the secondary winding of ignition transformer 16,which in turn causes a spark to be generated at spark plug 18. Theenergy which is not utilized in the spark is returned to capacitor 15with reverse polarity, since ignition capacitor 15 and ignitiontransformer 16 form a resonant circuit. When the current of thisresonant circuit passes through zero, the remaining energy is completelystored in capacitor 15 and the second thyristor 17 blocks. Because ofdiode 19 which has the inverse polarity to thyristor 17, the energystored in the capacitor is again available to primary coil 160, thuscausing the spark at spark plug 18 to continue past its otherwiseexisting time period. The length of the spark is almost doubled.

Inductive impedance 14 together with diode 19, effect automaticregulation of the required primary voltage. For example, if a great dealof energy is required for the spark, the remaining energy stored inignition capacitor is small and the voltage difference appearing betweenthe two terminals of inductive impedance 14 at the beginning of the nextenergy transfer between capacitors 12 and 15, is low. Thus, during thenext energy transfer, the voltage at the ignition capacitor 15 greatlyexceeds the supply voltage across capacitor 12, so that a high voltageis available for the next ignition, thus supplying a higher energy tothe next ignition. However if an ignition process requires only littleenergy, the remaining voltage on capacitor 15 remains relatively large,causing the voltage difference at the two terminals of inductiveimpedance 14 to be small, so that the voltage across ignition capacitor15 does not exceed the supply voltage by much. Thus a small amount ofelectrical energy is transferred from storage capacitor 12 to ignitioncapacitor 15. Such automatic regulation is particularly desirable when aseries of sparks is to be generated in rapid sequence, since it insuresreliable ignition of the fuel-air mixture in the cylinder and a highefficiency of the engine.

The capacitance of storage capacitor 12 greatly exceeds the capacitanceof ignition capacitor 15. It may be exceeded by much more than a factorof 10. This causes the charging of each ignition capacitor to cause onlya partial discharge of the storage capacitor, and therefore keeps thelosses generated in stage 11 during the charging of the storagecapacitor at a minimum. Low losses result when the voltage at thestorage capacitor 12 is a maximum prior to charging, thus causing littlecharging current to flow through stage 11, keeping the losses in thestage generated by its internal impedance at a minimum.

The circuit of FIG. 2 will now be discussed. Elements which correspondto the elements of FIG. 1 have the same reference numeral. Thedifference between the circuit of FIG. 2 and that of FIG. 1 is that theinductive impedance 14 is replaced by a second primary winding a of theignition transformer which is labelled 20 in FIG. 2. The ignitiontransformer has a first primary winding 20b which is connected toignition capacitor 15 via a thyristor 17 as in FIG. 1. However, asstated above, the second primary winding 20a is connected to the cathodeof thyristor 13 on one end, and to ignition capacitor 15 at the otherend. The secondary winding 20c of the ignition capacitor is againconnected to spark plug 18.

In the arrangement of FIG. 2, a spark is generated at spark plug 18 bothwhen energy is transferred from capacitor 12 to capacitor 15, and whencapacitor 15 is discharged through winding 20b. Thus in this particularcase, thyristors 13 and 17 are alternatingly put into the conductivecondition at the ignition time. Here, too, the diode 19 connected inparallel with thyristor 17, but with opposite polarity, effectsautomatic regulation of the required ignition voltage. This is the casesince, here, too, energy remaining on capacitor 15 after one ignition,causes less energy to be drawn from storage capacitor 12 prior to thesubsequent ignition. The main advantage of this ignition arrangementrelative to that of FIG. 1 is that the losses during transfer fromcapacitor 12 to capacitor 15, are only half of those of the arrangementof FIG. 1, since the frequency of energy transfer is half that of FIG.1.

FIG. 3 shows another preferred embodiment of the present invention.Again, the components in FIG. 3 which are the same as those of FIGS. 1and 2, have the same reference numbers. In the arrangement of FIG. 3, asecond ignition transformer, 21, is present. The primary winding, 21a,of ignition transformer 21, is the inductive impedance connected inseries with thyristor 13. The secondary winding 21b of the ignitiontransformer 21 also has a spark plug connected thereto. The ignitionarrangement of FIG. 3 operates similarly to that of FIG. 2.

Thyristors 13 and 17 are switched alternatingly to the conductive state,each at the ignition time. The control of thyristors 13 and 17 may takeplace by a control voltage furnished at the respective gates by means 23shown in FIG. 3 such as a multivibrator or a magnetic pulse generator.The spark frequency of the arrangement according to FIGS. 2 and 3 istwice as high as that of FIG. 1. In the arrangements of FIGS. 2 and 3,the diode 19 does not serve to lengthen the pulse which is generated atthe time of energy transfer between capacitors 12 and 15, since it iseffective only upon discharge of the ignition capacitor through theprimary winding of the ignition transformer. Thus diode 19 inarrangements of FIGS. 2 and 3, is only effective for every alternatespark. However, this is very advantageous in double-spark or multi-sparkignition arrangements, since the first spark may be made particularlyshort and of high energy by means of an appropriate design of theprimary winding 200 or 21a. The second spark is then made substantiallylonger and weaker by a corresponding design of the primary windings 20band 16a.

It is also within the scope of this invention that diode 19 can beomitted, thus causing all the sparks to be of equal strength andduration.

While the invention has been illustrated and described as embodied in acapacitive type ignition arrangement for internal combustion engines, itis not intended to be limited to the details shown, since variousmodifications, structural and circuit changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. In an internal combustion engine, an ignition arrangement,comprising, in combination, storage capacitor means; ignition capacitormeans; first switch means connecting said storage capacitor means tosaid ignition capacitor means when in a conductive state; first ignitiontransformer means having a primary winding connected in series to saidfirst switch means and a secondary winding; first spark generating meansconnected to said secondary winding; second ignition transformer meanshaving a primary winding and a secondary winding; second sparkgenerating means connected to said secondary winding; and second switchmeans connecting said primary winding of said second transformer meansin parallel with said ignition capacitor means when said second switchmeans is in a conductive state.

2. In an internal combustion engine, an ignition arrangement,comprising, in combination, storage capacitor means; ignition capacitormeans; first switch means connecting said storage capacitor means tosaid ignition capacitor means when in a conductive state; ignitiontransformer means having a first primary winding connected in series tosaid first switch means, a second primary winding, and a secondarywinding; and second switch means connecting said second primary windingto said ignition capacitor means when said second switch means is in aconductive state.

3. In an internal combustion engine, an ignition arrangement,comprising, in combination, storage capacitor means having a first andsecond terminal; ignition capacitor means having a first terminaldirectly connected to said first terminal of said storage capacitormeans and a second terminal; first switch means connecting said secondterminal of said storage capacitor means to said second terminal of saidignition capacitor means when in a conductive state; inductive impedancemeans series-connected to said first switch means; ignition transformermeans having a primary winding and a secondary winding; spark generatingmeans connected to said secondary winding; and second switch meansconnecting said primary winding in parallel with said ignition capacitormeans when said second switch means is in a conductive state,

4. An arrangement as set forth in claim 3, further comprising meansalternatingly switching said first and second switch means to saidconductive state.

5. An arrangement as set forth in claim 3, wherein said second switchmeans comprise a thyristor.

6. An arrangement as set forth in claim 5, further comprising diodemeans connected, with opposing p0- larity, in parallel with saidthyristor.

7. An arrangement as set forth in claim 3, wherein said first switchmeans comprise a thyristor.

8. An arrangement as set forth in claim 3, wherein the capacitance ofsaid storage capacitor substantially exceeds the capacitance of saidignition capacitor means. i

9. An arrangement as set forth in claim 8, wherein the capacitance ofsaid storage capacitor means is more than ten times the capacitance ofsaid ignition capacitOI means.

1. In an internal combustion engine, an ignition arrangement,comprising, in combination, storage capacitor means; ignition capacitormeans; first switch means connecting said storage capacitor means tosaid ignition capacitor means when in a conductive state; first ignitiontransformer means having a primary winding connected in series to saidfirst switch means and a secondary winding; first spark generating meansconnected to said secondary winding; second ignition transformer meanshaving a primary winding and a secondary winding; second sparkgenerating means connected to said secondary winding; and second switchmeans connecting said primary winding of said second transformer meansin parallel with said ignition capacitor means when said second switchmeans is in a conductive state.
 2. In an internal combustion engine, anignition arrangement, comprising, in combination, storage capacitormeans; ignition capacitor means; first switch means connecting saidstorage capacitor means to said ignition capacitor means when in aconductive state; ignition transformer means having a first primarywinding connected in series to said first switch means, a second primarywinding, and a secondary winding; and second switch means connectingsaid second primary winding to said ignition capacitor means when saidsecond switch means is in a conductive state.
 3. In an internalcombustion engine, an ignition arrangement, comprising, in combination,storage capacitor means having a first and second terminal; ignitioncapacitor means having a first terminal directly connected to said firstterminal of said storage capacitor means And a second terminal; firstswitch means connecting said second terminal of said storage capacitormeans to said second terminal of said ignition capacitor means when in aconductive state; inductive impedance means series-connected to saidfirst switch means; ignition transformer means having a primary windingand a secondary winding; spark generating means connected to saidsecondary winding; and second switch means connecting said primarywinding in parallel with said ignition capacitor means when said secondswitch means is in a conductive state.
 4. An arrangement as set forth inclaim 3, further comprising means alternatingly switching said first andsecond switch means to said conductive state.
 5. An arrangement as setforth in claim 3, wherein said second switch means comprise a thyristor.6. An arrangement as set forth in claim 5, further comprising diodemeans connected, with opposing polarity, in parallel with saidthyristor.
 7. An arrangement as set forth in claim 3, wherein said firstswitch means comprise a thyristor.
 8. An arrangement as set forth inclaim 3, wherein the capacitance of said storage capacitor substantiallyexceeds the capacitance of said ignition capacitor means.
 9. Anarrangement as set forth in claim 8, wherein the capacitance of saidstorage capacitor means is more than ten times the capacitance of saidignition capacitor means.